1. Field of the Invention
The present invention relates to techniques for determining write patterns for maskless-lithography processes that use write devices.
2. Related Art
Lithography processing represents an essential technology for manufacturing Integrated Circuits (IC) and Micro Electro-Mechanical Systems (MEMS). Lithographic techniques are used to define patterns, geometries, features, shapes, etc. (henceforth referred to as ‘patterns’) onto an integrated-circuit die, semiconductor wafer, or chips, where the patterns are typically defined by a set of contours, lines, boundaries, edges, curves, etc. (henceforth referred to as ‘contours’), which generally surround, enclose, and/or define the boundary of the various regions which constitute the patterns.
Existing lithographic techniques include photolithography, in which images defined by photo-masks are printed onto the integrated-circuit dies or the semiconductor wafers. Unfortunately, it is increasingly difficult to design and manufacture photo-masks. In particular, demand for increased density of features on these dies and wafers has resulted in the design of circuits with decreasing minimum dimensions. However, due to the wave nature of light, as dimensions approach sizes comparable to the wavelength of the light used in the photolithography process, the resulting wafer patterns deviate from the corresponding photo-mask patterns and are accompanied by unwanted distortions and artifacts.
Furthermore, the design and manufacture of photo-masks is time consuming and expensive. This poses a significant challenge during integrated-circuit development and for the production of small quantities of integrated-circuit dies or the semiconductor wafers.
In principle, maskless lithography offers a solution to at least some of these problems. In this technique, a write device directly prints a write pattern onto the integrated-circuit dies or the semiconductor wafers, thereby eliminating the need for photo-masks.
For example, researchers are investigating the use of spatial-light modulators, such as arrays of adjustable mirrors, in write devices. These spatial-light modulators may be configured to define the write pattern on at least a portion of the integrated-circuit dies or the semiconductor wafers. Unfortunately, existing techniques first determine mask patterns, which are then converted into write patterns. This is cumbersome and often ignores characteristics of the spatial-light modulators when the mask patterns are determined. Furthermore, the bifurcated-design technique may make it more difficult to improve resolution and/or a process window in a lithography process by appropriately pre-distorting the write pattern (using techniques such as Optical Proximity Correction or OPC) such that the wafer pattern is printed more accurately.
Hence, what is needed is a method and an apparatus that facilitates determination of write patterns without the above-described problems.